no problem in interpretation..
but results are not coming fine.
I have checked the face center and cell center value of u at that boundary, they are coming same, like for symmetry boundary condition.
Please help me in finding the bug in the udf.

You may also want to check BOUNDARY_FACE_GEOMETRY in the manual to improve the approximations in the UDF above; indeed it is assumed that the wall parallel velocity is along the x direction. A more correct implementation should first obtain the wall parallel velocity from the full 3D one, use this one to define the velocity at the wall from the specified wall normal gradient (also accounting for grid non-orthogonalities) and then project this velocity back to the three coordinates. This UDF provides you all the ingredients to accomplish the task, you just need to put in some vector algebra.

However, in the wall panel you also have the option to directly specify the shear at the wall, making the above UDF actually not required.

Rahul123

December 24, 2012 12:14

If I have to write a UDf for du/dy=0. Can I write it as F_PROFILE(f, t, i) = C_U(F_C0(f,t),THREAD_T0(t));